Like DNA work at crime scenes, we are using identical approaches to ask questions about evolution, writes ANTHONY KING
MATTHEW Jebb was named as director of the National Botanic Gardens last year, but this isn’t his first lead role. For six years, Jebb headed a botanical research institute in Papua New Guinea, surrounded by tropical jungle and far from these leafy and picturesque gardens on Dublin’s northside.
Like any good botanist, Jebb collected plants and brought dried specimens back to Ireland. From these he has now described five tree species new to science from the rainforests of Papua New Guinea.
They are a striking tree not least because of their big, fist-sized fruits that are scattered all over the forest floor. The fruits of these Barringtonia trees are fed upon by cassowaries, but these large flightless birds, which stand over five feet tall and are renowned for their aggression, were absent near the institute.
“Wherever you are near human habitations some of these big animals are missing because they have been eaten,” he explains. Without the cassowaries (big birds), the tree fruits remain untouched.
The reference specimens for the five new trees lie in a red-bricked building in the gardens, the herbarium, a cross between a botanical museum and a library. The herbarium is home to three-quarters of a million dried plant specimens.
“Many were collected in Ireland, but the majority were collected elsewhere, mainly from the tropics. Some of our particular strengths in the collection area are areas such as Australia and China,” he says.
Botanists can use this important world-class collection to compare living flora with dried plants collected during some of the earliest expeditions across Australia. “Although they are 200 years old, they are like an old book and perfectly accurate,” Jebb says.
A major contributor to the collection was Irish botanist Augustine Henry who lived in China from 1882 to 1900 and sent back plants previously unknown to science.
FORENSIC BOTANY
Pressing plants and preserving them dried is classic old-school botany, but the herbarium sees some flashy new science too. It is home to a DNA sequencing machine.
“Like DNA work at crime scenes for forensics, we are using identical approaches to ask questions about evolution and about relationships between different plants, seeing if we can identify plants accurately using genetic information,” Jebb explains.
Genetics has thrown up controversies, however. DNA analysis showed that foxgloves are closely related to plantains, the garden weeds, which Jebb describes as “astonishing”, and nettles are the dowdy first cousins of roses.
Gardens’ researcher Dr Colin Kelleher is looking into the disease resistance genes in Irish willow, using genetics to see how our native willows might fare as biofuel crops. “A lot of the clones used in biomass production are from Sweden and the UK,” says Kelleher, but it is likely that Irish trees are better adapted to diseases here.
“The commercial interest would be to develop our own clones and have Irish breeders do that. It could be a self-sustaining industry.” The project, funded by Teagasc and in collaboration with Trinity, takes in the native goat willow and widely planted osier willow.
Away from the dried plants and lab benches, “the Bots” – as the garden is often called – has been hosting an experiment for the last 40 years. It holds a “phenology” collection that consists of trees and shrubs planted in the 1960s and followed ever since.
Phenology is the measurement of changes in the biological calendar, such as when buds burst, when a flower opens, when seeds set or when swallows migrate.
Genetically identical trees and shrubs were planted in Italy, Germany, Norway and Spain, so scientists know it is the environment not the genes that is responsible for any changes.
And results are already in. “The growing season has lengthened by three weeks over the last 40 years,” says Jebb. Some tree species are holding their leaves three weeks longer in the year, opening 10-12 days earlier and dropping off 10-12 days later. So there is evidence for our changing climate.
FERN CRAZE
The Killarney fern has been cultivated in the Botanic Gardens for over 150 years. It’s a demanding tenant, requiring a cool, shady moist environment, and isn’t on public display right now. But Bots scientists are working on its cultivation.
It is exceptionally rare in the wild because of a fern collection mania. “The damage the Victorian fern collectors did is still being felt to this day. Many varieties they described are incredibly rare,” Jebb explains. “The Killarney fern is one of the saddest casualties.”
Hundreds of thousands of the plants were collected. Torc Waterfall in Kerry once had an acre of these filmy ferns, but now there are just three, he says.
PhD student Emer Ni Dhuill has become an expert in this plant. She showed that juvenile plants could reproduce sexually but she also grew wild-collected spores too, all of which suggests that the ferns have a future here.
Want to know more about what you can see at the National Botanic Gardens?
There are three audio tours and a smartphone app now available for the Gardens. The audio tours can be downloaded like a podcast, and the app and tours are free. Each tour has 40 minutes of commentary.
More information from the web site botanicgardens.ie
Pitcher plants the carniverous climbers that act like animals
THERE IS something particularly startling about a plant that eats like a carnivore. No sunlight or nutrients are needed to feed pitcher plants, they require meat to thrive. "Pitcher plants are very exciting because they bridge that gap if you like between the plant and animal kingdom," says Jebb.
"Here is a plant that behaves like an animal in that it is eating insects. Children and adults are equally fascinated by something that is so unusual."
Jebb is a world authority on these carnivorous climbers and he has described species of pitchers from Sumatra, the Philippines and Borneo.
Unfortunately their striking appearance and feeding habits make them a popular target for those set on making a fast euro. The pitcher plants of Asia aA(Nepenthes) are modern-day collectables and once retrieved from the wild there are plenty of collectors ready and willing to purchase them.
Some pitchers are actually under threat because of unauthorised plant hunting, Jebb says.
"Some of the new species I described back in 1997 have been threatened with extinction in the wild because of plant collectors tracking them down. It's difficult," he admits.
"As a scientist, I want to talk about new species and describe biodiversity, but there are others who might go there with the idea of making a profit. That can be disillusioning."
There is a big collection of pitcher plants in the Curvilinear range in the gardens, all of course coming to the gardens only via legitimate and authorised sources. As a major repository of and place for research on rare species, the collections held in places like the gardens and Kew in London become repositories where these unique plants can be kept safe.
They are climbers and are encouraged to growing up through rhododendrons at the gardens. There are quite a number on display, says Jebb, originating from India, Sumatra, Peninsular Malaysia, Borneo and New Guinea.
But he has no qualms about describing the new Barringtonia species. Nobody would be interested in taking away these large tropical trees as horticultural plants, he says.
– Anthony King
